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The elements numbered 57 to 71 have presented a problem in analytical chemistry unparalleled by that of any other group since their discovery over the span of the nineteenth century. The striking similarities in chemical behavior of the fifteen elements comprising this series have almost completely baffled analysts in every attack, and it is only with the increased use of those newer methods, best described as being of a strictly physical nature, that much real progress has been achieved. Where time-honored classical wet methods have failed rather disappointingly, newer methods based upon the use of the spectrograph and similar instruments have given much promise to the chemist interested in these elements. It is unfortunate that such determination leaves much to be desired in the way of quantitative accuracy, although as an orientation of purity, spectrographic data are of prime importance to the analyst. The problem, then, is to develop a method for the separation and determination of the rare earth elements based upon wet method techniques rather than upon the use of the spectrometer of other physical measuring instruments. The attack on the rare earth group as a whole would present almost insuperable obstacles to the worker pressed for time, and therefore only the elements comprising the cerium group have been chosen as a subject for research undertaken. As commonly accepted, this series consists of lanthanum, cerium, praseodymium, neodymium, element 61, and samarium. Europium might also be included, but its nature is much that of a transition element between the cerium and yttrium groups. The cerium group has been chosen because of the ready availability of the various salts (except those of element 61, of course) and because of the rather wide occurrence of the member elements in such minerals as monazite. Had time been available, an additional reason might have been the relatively simple spectre in the carbon or copper arc of these first elements of the whole rare earth series. Since most promise has been shown by the use of organic reagents, the greater part of the work has been done in this direction. An attempt has been made to select a representative cross-section of organic compounds used under a variety of conditions. Principal results are set forth in Table III of the appendix.

<p> The mineral eudialyte from Seal Lake, Labrador, was analyzed by means of x-ray fluorescence analysis for the rare earths La, Ce, Pr, Nd, Sm, Gd, Y and also for the element Zr. Samples were prepared by two methods: a) whole mineral powder being compressed into pellets, and b) the dissolved mineral being put through an ionic exchange process to eliminate interfering ions before compressing into pellets for analysis. The results are compared with published data.on other eudialyte occurrences. </p> / Thesis / Bachelor of Science (BSc)

The rare earths form series of compounds which are known for several elements but end abruptly or undergo a change of structure at some member of the series. The diantimonides are one such series. Sb-Sb repulsion becomes stronger as the rare earth size decreases and the previously known series ended at Sm. It was felt that high pressure would overcome the Sb-Sb repulsion and allow bonding to form stable or metastable compounds not possible by ordinary techniques. Synthesis studies were carried out on mixtures of antimony with all the rare earths except Pm and with Sc and Y. The known diantimonide series was extended two elements to GdSb2 and TbSb2. A new orthorhombic structure was found in the series for GdSb2, TbSb2, DySb2, HoSb2, ErSb2, TmSb2 and YSb2. Attempts to synthesize diantimonides of Sc, La, Ce, Eu and Lu were not successful. Reaction products for one to two molar mixtures of rare earth to antimony were determined for all the elements studied as a function of pressure and temperature up to 70 kilobars and 1800 °c. Products were identified by their X ray diffraction patterns. Only Sb plus the rare earth oxide were found for La, Ce and Eu. The oxygen apparently migrated into the sample from the pyrophyllite tetrahedrons. For Sc and Lu only the monoantimonides plus Sb were found. Only LaSb2 type diantimonides were found for Pr, Nd, Sm and Yb. Complex reaction product diagrams were obtained for mixtures of Gd, Tb, Dy, Ho, Er and Tm with Sb. Two different orthorhombic structures were found for GdSb2 and TbSb2. All compounds in the rare earth - antimony systems were silver-grey and metallic in appearance. All reacted almost the same with acids, H2O and NH4OH but did not react with organic reagents. They were stable to the atmosphere. The density of each compound was determined. Most of the heavy rare earth sesquisulfides are known in a monoclinic form except Yb2S3 which is orthorhombic and Lu2S3 which is rhombohedral. The light rare earth sesquisulfides are commonly found in a Th3P4 type cubic structure. Dy2S3 is found in both cubic and monoclinic forms. Since the cubic form is more dense and higher coordinated it seemed probable that the monoclinic form of the heavy rare earth sesquisulfides could be converted to the cubic form by high pressure techniques. Dy2S3, Ho2S3, Er2S3, Tm2S3, Yb2S3 and Y2S3 were all converted to the cubic form at 77 kilobars and 2000 °C in a cubic press. Lu2S3 was about 50 per cent converted to the cubic form at these conditions. The results of this investigation suggest that other series of rare earth compounds could be extended by high pressure techniques and several possibilities are discussed.

Call number: LD2668 .T4 1985 A42 / Master of Science

No description available.

Published from 1985 to 1986, DC Comics’ Crisis on Infinite Earths created the expectation that each crossover will result in numerous deaths and alter the structure or history of the DC Universe. Since many of these changes, such as the death of a popular or iconic character, cannot be sustained long term, the success and influence of Crisis on Infinite Earths led to the erosion of the very elements that made it shocking. Entire worlds can be destroyed, but superreaders eventually suspect that no change is ever permanent and, as more iconic characters are revived or rebooted, death is no longer meaningful.